This invention relates to camera housing units and, in particular, a housing unit suitable for an outdoor surveillance or video monitoring camera.
Although surveillance cameras and protective housings therefor are known, various difficulties have been encountered with existing units on the market, particularly in connection with surveillance cameras used outdoors. Generally speaking, expensive surveillance cameras must be protected from damaging weather conditions when they are used outdoors. These cameras are generally protected by placing them in a housing that keeps the camera dry and free from dirt and dust. One difficulty encountered with surveillance cameras used outdoors arises from the need for a surveillance camera with a lens having a long focal length, for example 700 mm. Such lenses are very sensitive to any movement of the lens and a very slight movement during the picture taking process will make the picture unclear and even completely unusable. If there is a wind blowing and acting on the housing for the camera, the vibration of the housing can be transmitted to the camera and its lens, thus rendering the camera useless.
Another difficulty with known surveillance cameras arises from the use of clear plastic or Plexiglas to construct all or part of the housing. The use of a clear material is of course necessary for the camera to view the desired area from inside the housing. However, plastic and Plexiglas over a camera lens, and particularly a very precise lens designed to take a clear picture from a long distance, will cause distortion of the picture and this is particularly true after the housing unit has been in use for a period of time because hairline cracks soon develop in the plastic material. The use of clear glass would overcome this problem but up until now the use of such material has been found to be too expensive. It will be appreciated that if a glass dome or hemisphere is used in a surveillance camera system, it must itself be constructed to very close tolerances in order to avoid picture distortion.
Although spherical housing units for surveillance cameras are known for indoor units, they have not been used in the past for outdoor units, possibly due to the difficulty of manufacturing a spherical unit that can withstand outdoor weather conditions and that has the required features inside the dome to keep the camera in good working order. There is a distinct advantage to the use of a spherical housing unit outdoors in that a sphere is the best aerodynamic shape, that is, it provides the least wind resistance on average when one takes into account the fact that the wind can blow from any direction. Because of the smaller air resistance created by the sphere, a spherical housing unit is less likely to be damaged by high wind conditions and will not vibrate as much as a unit of a different shape might.
A known housing assembly for a surveillance camera is that taught in U.S. Pat. No. 4,320,949 issued March 23, 1982, to R. Pagano. The housing has an upper portion in the shape of a truncated dome over which rain water may flow. The bottom of the dome is a clear hemispherical member. The mounting for the surveillance camera is connected directly to the mounting for the upper portion of the housing so that any vibration of the housing will be transmitted directly to the camera and its lens. The housing unit is fitted with a fan to ventilate the housing and electrical heaters that are connected to a thermostatically controlled switch. When the temperature approaches freezing, the heaters are energized so as to heat the air in the housing assembly.
Another surveillance camera housing unit and support is shown in U.S. Pat. No. 3,732,368 issued May 8th, 1973 to Telesphere Technology, Inc.. This patent discloses a spherical housing for a T.V. camera that can be both tilted and panned for viewing. The tilting motor tilts both the T.V. camera and the spherical enclosure, the latter being attached to a circular disk member that divides the housing in half. The camera lens views the outside through a small circular orifice covered by a screen. The panning motor is located outside the housing and may indeed be positioned above a ceiling member. The single panning motor rotates both the housing and the camera as a single unit.
Another spherical housing unit for a camera is taught in U.S. Pat. No. 4,225,881 issued Sept. 30, 1980 to Murray Tovi Designs, Inc.. The global housing is internally coated with a transparent nichrome layer that bonds a layer of highly reflective metal to the globe. A slot or transparent window is provided in the globe for the camera lens to see through. A highly sophisticated method is required to manufacture this globe.
Another U.S. patent that employs a spherical enclosure for a surveillance camera is U.S. Pat. No. 3,720,147 issued Mar. 13, 1973 to Setronics Corporation. The unit is designed for use in a store and can be attached to the ceiling of the store by means of a single pipe. The spherical shell is constructed from two complementary parts that can be made by molding transparent plastic sheet material such as Plexiglas. The interior surface of the housing is coated with a black paint except for an elongate window through with the camera views the surrounding area. The unit is fitted with separate scan and tilt motors for changing the position of the camera.